Field of the Invention
The inventions disclosed and taught herein relate generally to heating and cooling systems and method of use during surgery and, more specifically, relates to a system and method of use for the controlled heating and/or cooling of an internal organ or tissue of a patient before and during surgery.
Description of the Related Art
Under normal circumstances, the human body maintains a near-constant temperature of about 37 degrees Celsius (° C.) or about 98.6 degrees Fahrenheit (° F.), thereby maintaining a delicate balance that optimizes cellular functions and biochemical reactions, while simultaneously balancing the heat lost to the environment by heat produced within the body.
There are a number of instances, however, where medical intervention is required to manipulate the core human body temperature of a patient. Particularly, there are circumstances under which a patient will need to be cooled in a rapid manner to thwart the onset of serious, and often fatal, repercussions. For instance, a patient may be suffering from malignant hyperthermia, a life threatening elevation in body temperature experienced by some patients after receipt of certain muscle relaxants and general anesthetics during surgery. This situation is called a pharnacogenetic reaction; a variation in drug response caused by hereditary factors. Such a rapidly progressive reaction is often fatal, and requires immediately initiated treatment. This condition can be reversed if the patient's core body temperature is immediately lowered to within acceptable parameters.
By slowing down a patient's metabolism, the demand for oxygen and nutrients can be minimized until appropriate treatment is effectuated. A dangerously high core body temperature is often due to infection, tumor necrosis, or malignant hyperthermia.
Such conditions result in harmful fluid and electrolyte imbalances, increased cellular metabolic rates, and cognitive impairment. If not immediately addressed, a patient may suffer irreversible cellular injury, loss of brain and liver cells, and ultimately may suffer critical organ failure resulting in death.
Evidence suggests that patient cooling provides beneficial protection against further deterioration of patient health in instances of cardiac arrest, surgery on the brain blood vessels, stroke, traumatic injury, or open heart operations. Cooling the blood before or during such events has been found to substantially decrease the severity of the resulting injury to the patient.
The introduction of moderate hypothermia (28° C. to 32° C.) before cardiac arrest has been successfully used since the 1950's to protect the brain against the global ischemia that occurs during some open-heart surgeries. Recently, the American Heart Association and others have recommended that some victims of heart attacks be chilled using induced hypothermia [Polderman, K., Intensive Care Medicine, Vol. 30(4), pp. 556-575 (2004)]. There are about 250,000 to 300,000 people suffering from cardiac arrest in the United States yearly, with about 50,000 to 75,000 making it to the hospital with adequate time for blood cooling to protect the brain and heart from further injury. The International Liaison Committee on Resuscitation (ILCOR) ALS (Advanced Life Support) Task Force has recommended, in view of this and other information, that such cooling is beneficial for cardiac arrest patients, as well as patients suffering from other cardiac rhythm disorders [Nolan, J. P., et al., Circulation, Vol. 108, pp. 118-121 (2003)].
Although the benefits of patient cooling are well known, existing methods and systems are cumbersome, ineffective, and often inadequate for rapid patient cooling. Often, these cooling methods use an average “weight load” for a patient, which can result in over-shooting the desired temperature range, which in turn can lead to problems in correcting the temperature, and in some instances, harm to the patient as a result of the temperature over-shoot.
Current methods of cooling treatment include crude improvised solutions such as packing a patient in ice; immersing the patient in cool water; applying ice packs to the groin, axillae, neck, and other regions of the patient; or the use of a cooling helmet [Hachimi-Idrissi, S., et al., Resuscitation, Vol. 51, pp. 275-281 (2001)]. Naturally, it is seen that such techniques, although well-intentioned, do not provide for rapid body temperature cooling as often required in surgery and Intensive care situations. Such treatment is difficult and labor intensive and cannot be performed in medical cases where time is of the essence.
Other attempts at patient cooling have included convective thermal blankets, room coolers, and other similar external cooling mechanisms. Although such devices do assist in cooling the environment surrounding a patient, they are generally ineffective in adequately reducing a patient's core body temperature, and do not allow for any control of the cooling of a patient. Furthermore, such methods generally produce unwanted patient shivering and discomfort which may even lead to an increase in core body temperature.
Evaporative cooling has also been attempted by wetting a patient's skin or clothing and allowing the water, or other liquid, to evaporate and remove heat from the body. Such treatment generally includes sponge baths and is sometimes combined with enhanced room air circulation to increase the rate of evaporation. Such cooling is not practical in intensive care situations, is extremely time-consuming and labor intensive, and inadequate for serious life-threatening conditions.
A variety of surgical patient blood cooling methods and systems are also available. Such treatment generally involves the use of cooling catheters inserted into a vein for direct cooling of a patient's blood through the use of cooled saline, wherein the saline cools the patient's whole body by lowering the temperature of a patient's blood at a rate of about 1° C.-2° C/ hour. The intravenous infusion of crystalloid at 4° C. over time to reduce core temperature has also been described [Bernard, S., et al., Resuscitation, Vol. 56, pp. 9-13 (2003)]. Such devices and approaches, while efficient, are invasive and require surgical incision. The invasive surgical treatment required by such devices require substantial time and skill to administer properly, force patients to undergo additional pain and discomfort, introduce the risk of contamination and blood clotting, and have been cost-prohibitive and impractical in use. Other adverse events associated with this type of technique include bleeding, infection, vasculature puncture, and the potential for deep vein thrombosis (DVT) [See, for example, Simosa, H. F., et al., The American Surgeon, Vol. 73 (5), pp. 461-464 (2007)].
In these respects, the patient cooling system for medical treatment of the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing, provides a system and method capable of both reducing and elevating patient body and organ temperature in a controlled yet substantially safe, cost-effective, and practical manner.
The inventions disclosed and taught herein are directed to an improved system for both heating and/or cooling a patient during a surgical procedure, as well as an improved thermoelectric device capable of both cooling and heating.